470 TUMORS. 



expense of the surrounding tissue ; it then bears the name of a malignant 

 tumor. We do not know where this capacity for infecting is located. Malig- 

 nant tumors have the property of producing their own kind in internal organs, 

 mostly in the lungs and the liver, although often their origin was far from 

 these organs. The inference is that particles of the tumor are carried as 

 emboli by the vascular system of these organs, and being fixed there, owing 

 to the narrow capillaries, increase and involve the tissue in which they are 

 lodged. Cohnheim and Maas * have attempted experimentally to prove the 

 presence of embolisms by transferring pieces, freshly cut from the periosteum 

 of a dog, into the jugular vein of the same animal. Between the tenth and 

 sixteenth day after the experiment they found the periosteal pieces embolized 

 in the lungs, and exhibiting all the features characteristic of a new formation 

 of bone-tissue. In animals which were killed after the twentieth day they 

 found the pieces of periosteum shriveled, and no trace of ossification or of a 

 neighboring inflammation. The above-named observers claim that their 

 experiments prove the possibility of proliferation of cancer emboli, and, as 

 they were not successful with scraps of periosteum, they concluded that indi- 

 viduals with generalized tumors lack the capacity of removing useless mate- 

 rial from the organism. 



S. Strieker t analyzes these results, and gives the following summary : (a) 

 Question: Are emboli of tumors capable of growing into tumors? (b) Experi- 

 ment : Emboli of periosteum have perished, (c) Conclusion: Emboli of 

 tumors, therefore, do not perish. 



Repeated experiments have been made to infect dogs, by transferring 

 particles of freshly extirpated malignant tumors of man, by inoculation, or by 

 injection into the vascular system. C. O. Weber and B. v. Langenbeck have 

 reported positive results. But as these results are so few in comparison with 

 the failures of many other experimenters, and, in addition to this, dogs are 

 known to be frequently subject to malignant growths, the conclusions derived 

 from such experiments must be received with caution. 



Composition and Localization. In the composition of tumors 

 connective tissue always enters, this structure being the carrier 

 of blood-vessels. The character of the tumor depends greatly upon 

 the amount of connective tissue present, its stage of develop- 

 ment, and its combination with other varieties of tissue, such as 

 muscles, nerves, and epithelia. There is a class of tumors which 

 are composed entirely of connective tissue and its derivations, 

 and exhibit a simple type of construction ; by Virchow these are 

 termed simple Mstoid tumors. Another class shows combinations 

 of several tissues, imitating, to some extent, the structure of cer- 

 tain organs of the body, and Virchow proposes for their designa- 

 tion the name organoid tumors. In a third variety of tumors 

 the structures of different organs are incompletely represented, 

 and such growths are called by Virchow teratoid tumors. Lastly, 



* Virchow's Archiv. Bd. Ixx. 



t " Vorlesungen iiber allg. u. exper. Pathologic." Wien, 1878. 



